Examples include trophoblast (Greek blastos, germ, sprout), a layer of tissue on the outside of a mammalian blastula, supplying the embryo with nourishment; trophozoite (Greek zoion, animal), a growing stage in the life cycle of some sporozoan parasites, when they are absorbing nutrients from the host; trophallaxis (Greek allaxis, exchange), the mutual exchange of regurgitated liquids between adult social insects or between them and their larvae.